Brake control valve



Aug. 5, 1952 A. DEWAN DRE BRAKE CONTROL .VALVE 2 SHEETS7-SHEET 1 Filed April 1'7, 1946 In v 6177C0i? fie zu a/12/&19e

5, 1952' A. DEWANDRE 2,606,077

BRAKE CONTROL VALVE Filed April 17, 194 2 SHEETS-- SHEET 2 Patented Aug. 5, 1952 2,606,077 BRAKE CONTROL VALVE AIbertDewandre, Brussels, Belgium Application April 17, 1946, Serial No. 662,900 r In Belgium June 19,1942

Section 1, Public Law 690, August 8,1946

Patent expires Junelfi, 1962 J 1 My invention concerns means for the automatic braking of trailers by means of compressed air and in particular improvements in the control oi the reaction distributing valves provided on the tractor and of the emergency valve on the trailer with the object of controlling the brakes and providing automatic action in case oi breaking of the couplings.

In hitherto existing arrangements of thisnature when a certain amount of'brakingis applied corresponding to a given position of the brake pedal, the driver is obliged to maintain the pedal in this position without any variation being allowed to avoid unstable braking of the trailer. This instability-arises from slight angular movements of the pedal producing an alternative opening and closing of the air escape and admission valves on the distributor with consequent variations in the pressure in the pipe line of the system.

The idea of the invention is to avoid the inconveniences arising from these slight variations of engine torque on the distributor valves and the consequent slight variations of pressure in the pipe system.

The invention consists in providing a certain time lag to the opening or closing of one of the 7 two escape or admission valves with relation to the other by means of a certain clearance provided between the elements connecting the aforesaid valves. 1

Some examples of what the invention eiiects will be described in the following description in conjunction with the accompanying drawings, e; g.:

Figure 1 shows diagrammatically an arrangement of an installation for braking trailers.

Figure 2 is a longitudinal. section of .a reaction distributor comprising the invention.

Figure 3 is a cross-section of the same distributor.

Figure 4 is a detail view of Figure 2 showing a modified position ofone of the valves.

Figure 5 is a sectional view of an emergency valve for trailers comprising the invention.

Figure 6 is a view similar to Figure 5 showing one of the valves in a modified position.

As shown in Figure 1, the arrangement of trailer brake system'carried on the tractor is; a compressor l0, supplying a main reservoir ll through a pipe system l2, in which is situated an oil separator l3, and a pressure regulator '14. A reaction distributor l5 controlled by a brake pedal 9 is connected on the one hand to the reservoir l I and on the other hand to the pipe system 7 1 Claim. (Cl. 30328) I in which is situated a stop valve IS. A flexible pipe l9 connects the pipe system I! to the trailer.

The trailer mechanism comprises an auxiliary reservoir 20 connected on the one side to the pipe I! through a non-return valve 20A and on the other side to an emergency valve 2| which inits turn is connected by means of a three-way valve Z2'to the pipe system H. The brake cylinders 23and 24 of the trailer'are connected by a pipe system 25 to the emergency valve 2|.

As shown in Figures 2 to 4, the reaction distributor l5 constructed according to the invention comprises an escape valve 26 and its spring 21; an admission valve 28, a piston 29 constituting the seating of this admission valve 28, a

exterior lever 33; a return spring 34 and a drag spring 35.

The chamber situated at the left of the piston 29 is rendered air-tight Where the shaft 3! (Figure 3) passes through by means of a washer 35 of elastic material interposed between the distributor boss and the shoulder in a side of the shaft 3|. The shaft is held against the washer 36 by means of the spring 3?. i

The air under pressure from the main reservoir H (Figure 1) enters the distributor l5 through pipe IS. The main pipe system is connected through I1 to the distributor which has an exhaust' 38 to the'atmosphere.

'During normal running (brakes released) the position of the various parts described is as follows:

The escape valve 26 is closed and held on its seating by the action of spring 21. By virtue of the position of the piston 29 the admission valve 28 is open and the main reservoir is in direct connection with the main pipe system. There is a space 39, the purpose of which will be explained later, between. the valves 26 and 28. Under the action of spring 34, the exterior lever 33, tends to move towards the right and thus maintains through interior lever 32 and gudgeon tem, including the distributor, is the same as that in the main reservoir. Two faces of the piston 29 are therefore under the same pressure.

The reaction distributor works in the following fashion.

Spring 35 between the.

If pressure is applied to the brake pedal the exterior lever 33 then moves to the left which by means of an interior lever 32 and gudgeon pin pulls the piston 29 also towards the left. Piston 29 then comes into contact with admission valve 28 which;-is.then; held against its-seating. The chambers on both sides of the piston 29 are thereupon isolated from each other and communication between the main reservoir and the pipe system is cut off. The pressure, however, on

both faces of the piston 29 is still the same. .Now,.;'

as soon as the admission valve 28 comes into contact with its seating it becomes virtually a part of" the piston 29. When piston 29 moves to theleft;

it will be seen that admission valve 28, aftertraversing the space 39 and coming into contact with v escape valve 26 opens the exhaust hole. 38. The

compressed air escaping into the atmosphere causes a drop in pressure on the right side of the piston. Due to the difference in pressure on either side, piston 29 immediately moves towards the right. It acts. then in the opposite.direction to,

the drivers pressure. The driver is compelled, if he wishes to. continue the braking action,- to

pressharder on the pedal. to keep piston 29 in position, ,=SQ.. that the .escape .valve will. remain open. a

Ifthe drivenkeeps hispedalin a constantprcssure-at-any pointof its travel pistonifl due-.to

thedifference in pressure pointed out above 7 and 9 also in consequence of thespring movestowards the right until escape .valve .26 makescontact with itsseat-andthus closes the exhaust hole 38 and isolates the pipe system from the atmosphere. At this moment admissionvalve 23 and escape -valve'2-6 being shut (FigureA) piston 29 stops in a position of equilibrium. v.Thepressure in thesystemthen becomes stabilized and Will-remain in this condition so long .as. the, pressure in the pedal does not vary.

The condition of equilibrium-of piston 29 mentioned above can-be defined as. follows: :tocompensate-the pressure acting upon the-leftface of thepiston29- due to thepressureirom the main reservoir (a constantpressure through-thecontinued-action'of the compressor) an additional force is required besides thattromthe: pressure in the pipe syst m a this is-1 rc ded ar-th driveracting on the;brake pedal. {Ihusthe more thezpressure; diminishes; on the: rightv side of the;

p ston inthe rip system. h sr at r must; be the pressure exerted on -;the pedal. In other Words: the reaction felt byth dr ver s: d pendent upon the dropping pressure in. the general pipe system. This effort is transmitted to the ;dis.-,

tributor through the elastic connection provided by the; spring. 3.5.

'In order; that pistonFZS: may stop in a-position of Y equilibrium; it, g-is absolutely necessary that admission and escape valves 26. andlZBshouldzboth be completelyclosedtiFigureA). 39 no longer exists between thevalves, piston-'29 must always take up .the same positionwhich .is carefullyworked out. :If by reason of: itsinertia,

piston :29 passes beyond .this position of-equilibrium a;dm-ission valve '2 8 opened and causes unstablenbraking. It'jiS. in ,order .to remedy: this:

inconvenience; that; thespace; 39 is provided. between the-valves.

It as be inted ou t a i -.1 a in piston 29 is underaconstant;tendency;towards the right 'due to the diii'ference of pressure acting on thetwofaces. In consequence: if the driver releases the brake; pedal, piston 29,- by moving towards the right, first of all closes the, escape When the space under'atmospheric pressure:

4 valve 26 which isolates the pipe system from the atmosphere, and then opens the admission valve 28 after traversing the space 39. The general pipe system is again put into communication with the main reservoir and refilled from it. All the parts of the distributor re-assume .theinpositions for normal working (Figure 2).

As is shown in Figures 5 and 6, the relay valve 2|, which controls operation of the trailer brakes and which also serves as an emergency valve in case of accidental brakeway of the trailer, comprisesalower piston 40, an upper piston 4| working against the pressure of a spring 42 and constituting theseating for an escape valve 43, under the action of spring 44 and an admission valve 2 45 under the action of spring 46.

The escape'valve 43,.adapted ,toclose passage .43

in piston.4|-, is.held against the.body. of the .valve 2| by its springs. Through the position of the piston-4 ,-escape valve.4-3- is open .and, establishes in this way throughgchambers;52,.passage 43', and,

chamber 59 communicationbetweenthe atmosphere and the .brake cylinders. The admission valve v45 is-heldon its seat bythe action-oi a spring 46 --A space-55 whose purpose willbe'explained later, is arranged between the escape valve 43 and the admission valve 45.

Through the intermediary of non-return valve 20A,-the-pipe system supplies, during .normal,

runningauxiliary reservoir 20. The air pressure inchambers 47 and 50 is thus the same. 'Sinceboth faces of the piston 40 are under the saine pressure, the piston is perfectly balanced. Chambers t2 and 53 being in communication ,with the atmosphere both faces of piston 4| are under atmosphericpressureandthe piston is onlybeing acted upon'by its spring 42 pressing 113583 151".

piston 40.

The. working of the emergen y .valv ris as {$01- lows:

Through the action of thereaction distributor situated on the tractor a fall of pressure takes;

place in thegeneral system. This shows in chamber 50; piston 40 due to thedifierence, of pressure on both faces acts-on-piston4l againstrthe -resistance of spring 42. --Piston,;4| is changing: its position, contacts the escape valve 43, which .is

pressed against its seating and in so doing interrupts communication between chambers 52 and 53. The brake cylinderis thusdsolated fromithe atmosphere. "The two faces o'fpiston- 4| arestill As soon as valve. is resting on itsseating it; becomes part of piston 4|. If themovement of the latter is observed, it will be seenithat escape valve 43, after travelling overspace 5 5, acts in its'turn upon admission valve '45, whichopens, and through the interim-- diaryofchamberA'l, piston 48 and chamber-53- putsauxiliary-reservoir 20 into communication with the cylinders 23 and Him applying-the trailer brak es.

(Jhamber5.3 being under the pressure of the compressed air from the auxiliary reservoir, piston 4| immediately moves in the opposite direction to that taken when acted upon by the piston 40. If one wishes to continue the braking action further the pressure in the pipe system must be allowed to drop still further and by so doing in chamber 50 to allow piston 40 to resist the action of piston 4| and holds the admission valve 45 in the open position. Thus during the braking action, piston 4| has a constant tendency to force piston 40 back to its starting point.

If the driver through the distributor aperture l5 maintains a constant pressure in the system H, piston 4| due to the unequal pressure caused by the always increasing force of the compressed air in chamber 53, neutralizes the action of piston 4|) and moves until the admission valve 45 comes into contact with its seating and interrupts the communication between auxiliary reservoir and the brake cylinders. At this moment the admission valve 45 and escape valve 43 both being shut (Figure 6) piston 4| stops in a position of equilibrium. From this moment the braking is stabilized and will remain thus so long as the pressure existing in the system does not vary.

The state of equilibrium of piston 4| may be defined as follows; the pressure exerted on the piston 4| by the pressure of the compressed air acting in chamber 53 must be compensated by the difference of the pressures acting on both faces of the piston which is subjected on the one hand to the pressure of the compressed air of the auxiliary reservoir, and the pressure existing in the pipe system. Thus, the more the pressure of the compressed air increases in the brake cylinders and through this in the chamber 53, the greater must be the drop in pressure in the pipe system. Which means that the action of the brake cylinders is dependent on the drop in pressure in the general pipe system H.

In order that piston 4| may stop in a position of equilibrium, escape valve 43 and admission valve 45 must be completely closed (Figure 6). When the space no longer exists between the valves, piston 4| must always assume one position only which has been determined. If, by reason of its inertia piston 4| travels beyond this position of equilibrium, escape valve 43 opens and causes unstable braking. It is to prevent this that space 55 is provided between the valves 43 and 45.

It has been pointed out that during the braking action, piston 4| constantly opposes the action of piston 40. As a result, if through the action of the reaction distributor on the tractor, normal working pressure is re-established in the system, piston 40, the twofaces of which are under the same pressure once more, re-assumes its initial position. Piston 4| under the action of the compressed air still acting in chamber 53 rejoins piston 40 and causes first the closing of the admission valve 45 thus isolating the brake cylinders from the auxiliary reservoirs 2|], and next, after moving across the space 55, opens the escape valve 43, allowing the compressed air in the brake cylinders to escape. The brakes on the trailer are then released and the working parts of the emergency valve re-assume their normal positions (Figure 5).

It has been pointed out that, in order to brake the trailer a drop in pressure is brought about in the pipe system. Should the couplings break, the compressed air in the system escapes entirely into the atmosphere, the braking action is then maximum and the trailer is instantly and automatically halted. In the working of the distributor fitted on the tractor it has been pointed out that the reaction felt by the driver is a measure of the drop in pressure of the general system. It has also been demonstrated in the working of the emergency valve situated on the trailer that the action of the brake cylinder is also dependent on the fall in pressure of the pipe system. It may be concluded therefore, that the force applied to the brake pedal is ameasure of the braking action. The harder the pedal is pressed, the greater will be the braking action on the trailer. In other words the driver can adjust the braking action as he pleases and maintain a perfect control over the brakes. The same effects hold good when slackening the brakes is required so that, adjustment is possible both in braking and slackening.

What I claim is:

In a distributor for automatic compressed air brake systems for trailers, forming an emergency valve for trailers, comprising in combination with an auxiliary reservoir, the general pipe system and the pipes of the brake'cylinders, a first cylinder, a piston in said cylinder to be submitted on the one hand to the pressure in the auxiliary reservoir, and on the other hand to the pres: sure in the general pipe system, a second cylinder, a piston in said second cylinder, a spring opposing to the displacements of the latter piston, a first chamber formed on one side of this piston and communicating with the atmosphere, a second chamber formed on the other side of this piston and communicating with the pipes of the brake cylinders, means for actuating the piston of said second cylinder when the piston of said first cylinder is moved, an opening in the piston of said second cylinder to establish the communication between the chambers formed on both sides of the latter piston, a first valve in said second cylinder andwhich is normally open, to co-operate with said opening when the piston in the second cylinder is displaced, an opposing spring acting on said valve, an opening in said second chamber to establish the communication between said second chamber and the auxiliary reservoir, a second valve for normally closing this opening, a spring acting on said second valve, and a connection with limited play between said first and second valves.

ALBERT DEWANDRE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,541,913 Bartholomew June 16, 1925 1,585,819 Barty et al. May 25, 1926 1,890,087 Kasantzeff Dec. 6, 1932 2,099,263 Farmer Nov. 16, 1937 2,267,122 McWhirter Dec. 23, 1941 2,281,138 Christensen Apr. 28, 1942 

